40 THE GASES IN ROCKS. 



piece is a hole large enough to permit the ready movement of the piston- 

 shaft. Around this hole on the upper side there is welded a short piece of 

 steel tubing which is to guide the piston-rod and serve as a place of attach- 

 ment for the rubber tubing in which the shaft of the piston is incased. 

 The piston is a shaft 50 centimeters in length, 2.2 centimeters in thickness, 

 to which is attached a head piece of hardened steel which will fit snugly 

 into the cylinder. Near the upper end of the piston is a cross-bar serving 

 as a handle, and also a flange to which the rubber tube is to be fitted. 



When ready to put together, the piston-shaft is incased in a 1-inch 

 tube of pure rubber, 45 centimeters long, which is tightly fitted and wired 

 to the flange near the end of the rod, whereupon the other end of the shaft 

 is slipped through the hole in the cover-piece, and the piston-head affixed. 

 The lower end of the rubber tube is wired to the steel tube of the cover- 

 piece which, after the rock specimen has been placed in the cylinder, is 

 fitted with a rubber washer and screwed as tightly as possible to the cylinder. 

 The rubber tube is taken of length sufficient to allow the head of the piston 

 to touch the bottom of the cylinder; by pulling upward on the handle the 

 rubber wrinkles and folds upon itself, affording ample play to the piston. 



The stopcock is connected with the mercury-pump and the cylinder of 

 the crusher exhausted, after which vigorous strokes delivered at the end of 

 the piston with a heavy mallet crush the rock, thus opening the gas cavities. 

 Whatever gas is liberated, is pumped into the receiver and analyzed in the 

 ordinary way. 



RESULTS. 



Of the first rock tested, a basalt from the Faroe Islands, 42 grams 

 were crushed finely enough to pass through a 30-mesh sieve, besides several 

 times as much, less completely pulverized. In all, less than 0.1 cubic 

 centimeter of gas was obtained, which may be considered as practically no 

 gas at all, since this small quantity is within the leaking possibilities of the 

 apparatus. 



A slightly scoriaceous basalt from Hawaii produced about 0.1 cubic 

 centimeter of gas, which appeared to be largely air. No carbon dioxide 

 could be detected. Of this basalt, 18.3 grams passed through the sieve. 



15.73 grams of vein quartz from Utah (No. 71 of the analyses) gave no 

 trace of gas. 



In an effort to demonstrate conclusively that the lack of gas liberated 

 by crushing these lavas was not due to defective apparatus, a glass bulb 

 of measured capacity, filled with air, was broken in the crusher in place of 

 the rock ordinarily used. The result showed that gas introduced into the 

 crusher can be extracted without sensible change in volume. As diffusion 

 through the rubber tubing was considered a possible, though not very 

 probable, source of error, a further trial was made, using hydrogen, lightest 

 and most active among the gases, in order to put the apparatus to as 

 severe a test as possible. The purity of this hydrogen had previously been 

 established by analysis. The bulb broken, the gas was pumped off and 

 exploded with air. The observed shrinkage agreed, within the limit of 

 error, with the amount of hydrogen calculated to have been contained 

 within the bulb. 



